Compositions and methods for protecting cells during cancer chemotherapy and radiotherapy

ABSTRACT

Compositions, pharmaceutical preparations and methods are disclosed for protecting non-neoplastic cells from damage caused by cancer chemotherapeutic agents or radiation therapy, during the course of cancer therapy or bone marrow transplant. These are based on the use of chemoprotective inducing agents that induce or increase production of cellular detoxification enzymes in target cell populations. The compositions and methods are useful to reduce or prevent hair loss, gastrointestinal distress and lesions of the skin and oral mucosa that commonly occur in patients undergoing cancer therapy. Also disclosed is a novel assay system for identifying new chemoprotective inducing agents.

This is a divisional of U.S. application Ser. No. 09/565,714, filed May5, 2000 now abandoned, the entire contents of which are incorporated byreference herein.

Pursuant to 35 U.S.C. §202(c), it is acknowledged that the U.S.Government has certain rights in the invention described herein, whichwas made in part with funds from the National Institutes of Health,Grant No. CA22484.

FIELD OF THE INVENTION

The present invention relates to the field of cancer therapy. Inparticular, the invention provides novel compositions and methods forprotecting non-neoplastic cells from the toxic effects of radiotherapyand cancer chemotherapeutic agents.

BACKGROUND OF THE INVENTION

Several publications are referenced in this application in order to morefully describe the state of the art to which this invention pertains.The disclosure of each of these publications is incorporated byreference herein.

Over the past several decades, chemotherapy and radiation therapycoupled with surgery have contributed to a significant reduction incancer mortality. However, the potential utility of chemotherapeuticdrugs in the treatment of cancer has not been fully exploited due toadverse effects associated with the nonspecific cytotoxicity of theseagents. Alkylating agents, used alone or in combination with otherchemotherapeutic agents, are used in approximately half of allchemotherapy treatments. Alkylating agents interfere with theproliferation of cancerous cells by inhibiting DNA replication.Non-alkylating cancer chemotherapy drugs are also toxic to mammaliancells; they can inhibit multiple sites within a replicating cell, suchas (1) synthesis of nucleotides required for DNA replication and (2)microtubule function required for mitosis, to name just two. Radiationtherapy, which achieves most of its cell killing properties bygenerating oxygen radicals within cells, can also efficiently killmammalian cells. Because the toxic effects of these three commonly usedagents are generally not specific to cancer cells, they also affect thegrowth of normal cells, particularly mitotically active normal cells. Asa result, persons being treated with one or more of these cancertherapies commonly develop numerous clinical complications.

Many populations of epithelial cells have a high turnover rate. Thetoxicity of cancer therapy for epithelial cells accounts for many of theside effects commonly suffered by persons undergoing a regimen ofchemotherapy or radiotherapy. These include gastrointestinal distress,nausea, vomiting, diarrhea, loss of appetite, hair loss, bone marrowsuppression and skin rash or ulceration at the site of irradiation.These complications can be so difficult to endure that it is notuncommon for people to forego or discontinue recommended cancer therapytreatments in order to avoid the problems. The gastrointestinaldisturbances may compromise a patient's chances of recovery, becausethey make it difficult for him to obtain the nourishment necessary tooptimize his ability to fight disease.

Typically, during the course of chemotherapy, the chemotherapeutic agentis administered in sub-optimal doses in order to minimize toxicity andto protect normal, drug-sensitive cells. Reducing the sensitivity ofnormal cells to chemotherapeutic agents would allow the administrationof higher drug dosages and chemotherapy could be rendered moreeffective.

The successful implementation of protective therapies that promoteroutine growth and proliferation of normal cells in the presence ofradiotherapy or chemotherapeutic agents will allow the use of higherdose aggressive chemotherapy. Two important targets for development ofsuch therapies are (1) the epithelial cells lining the entiregastrointestinal (GI) tract, including the oral mucosa, and (2) theepithelial cells of the skin, including hair follicles and theepidermis.

It appears that chemo- and radiotherapy-associated death and sloughingof GI lumenal cells results in a release of GI damage-associatedmolecules into the vasculature. These blood-borne molecules, whendetected by sites within the brain, trigger the nausea response that isso common among patients receiving chemotherapy. Present treatments withdrugs, such as Ondansetron, serve to suppress these brain centers andthus diminish the nausea response. However, the primary destruction ofthe GI lining still limits the most effective use of chemotherapy. Abetter mechanism to diminish nausea in these patients is to eliminatethe primary destruction of the GI surface and thus prevent the releaseof damage-associated, nausea-inducing molecules, rather than justsuppressing the effects of these molecules in the brain.

New gastrointestinal therapies are being developed that have affordedsome protection to normal cells and have maintained the integrity andfunction of the tissues made up of these cells. Current approaches toprotecting normal cells and stimulating proliferation of normal cellsinvolve nutrient stimulation and maximizing the intake of growthfactors. Such strategies have been shown to reduce the severity oftoxicity and/or shorten the course of drug treatment. However, in spiteof these improvements, serious side effects still persist and moreeffective therapies are needed.

Investigations have also been made into treatment ofchemotherapy-induced alopecia. Alopecia or hair loss is the most commonhair growth disorder in humans and is often the cause of great concernin affected individuals. In patients with acquired alopecia associatedwith cancer chemotherapy or radiation therapy, the loss of hair rankedabove vomiting as an important concern. Although this condition isgenerally reversible and regeneration of hair growth occurs within 1-2months after discontinuation of treatment, hair loss represents apsychologically distressing effect that can cause negative changes inbody image, decreased social activity and altered interpersonalrelationships and may lead to refusal of further chemotherapy.

The phenomenon of chemotherapy-induced alopecia is believed to resultfrom cytotoxic and apoptosis related damage to the hair follicle.Several studies have shown evidence that the pathobiologic mechanismsthat underlie chemotherapy induced follicle damage are characterized bybulging of the dermal papilla, kinking and distension of the follicularcanal and disruption of the melanogenic apparatus.

A variety of approaches have been employed in an attempt to protectpatients from chemotherapy-induced alopecia. These have includedphysical modules that temporarily decrease scalp blood flow and drugcontact time with the hair follicle, but the patient tolerance was verypoor. These poor results led to the development of scalp cooling methodsthat decrease both the metabolic rate of follicular stem cells and bloodflow to the follicle matrix but this strategy was found to beunsuccessful. The use of dietary α-tocopherol a free radical scavenger,was shown to have a protective effect in rabbits but not in humans.Minoxidil 2% solution was also found to be ineffective in treatingchemotherapy induced alopecia. Pre-treatment of rodents with growthfactors and cytokines provided some degree of protection againstalopecia induced by ARA-C (cytosine arabinoside) but not the commonlyused cancer drug cytoxan.

Reversal of cyclophosphamide-or cyclophosphamide/cytarabine-inducedalopecia by N-acetylcysteine (NAC) or NAC/ImmuVert, administeredparenterally or applied topically in liposomes, has been reported in arat model system (Jimenez et al., Cancer Investigation 10: 271-276,1992). NAC is a precursor of glutathione and, as such, is believed tofunction as a detoxifying agent by increasing intracellular GSH levels.This sort of therapy is limited in efficacy, inasmuch as it has beenshown that intracellular GSH levels can only roughly double in a cell byadding exogenous NAC. (See Ho & Fahl, J. Biol. Chem. 259: 11231-11235,1984; Carcinogenesis 5: 143-148, 1984).

U.S. Pat. No. 5,753,263 to Lishko et al. discloses methods andcompositions for treating alopecia induced by certain chemotherapeuticagents, which comprise topical application of an effective amount of ap-glycoprotein, or MDR gene encoding such a protein, in a liposomecarrier. This therapy is limited to the particular chemotherapeuticagents that can be exported from a cell via the p-glycoprotein pump.Notably excluded from this list are alkylating chemotherapeutic agents.

Thus, while treatments of the types outlined above may provide somerelief from chemotherapy-induced hair loss, their utility is limited,and additional effective therapies are needed.

SUMMARY OF THE INVENTION

In accordance with the present invention, a novel and effective strategyhas been devised for protecting rapidly dividing normal cells fromdamage during the course of radiation therapy or chemotherapy to treat acancer. This strategy is based on stimulating the natural detoxificationsystems present in the cells such that they are activated when radiationor chemotherapy is applied, and can thereby protect the cells fromdamage.

According to one aspect of the invention, a composition for protectingnon-neoplastic cells from damage during cancer chemotherapy orradiotherapy is provided. The composition comprises one or morechemoprotective inducing agents, as defined hereinbelow, and a deliveryvehicle for delivering the agents to a target population of thenon-neoplastic cells. In one preferred embodiment, the target cellpopulation comprises epithelial cells lining hair follicles orcomprising the skin epidermis. In another preferred embodiment, thetarget cell population comprises epithelial cells of the oral mucosa andgastrointestinal lumen.

According to another aspect of the invention, a method is provided forprotecting non-neoplastic cells from damage during cancer chemotherapyor radiotherapy. The method comprises administering to a population ofepithelial cells a composition as described above, for a time and in anamount effective to protect the non-neoplastic cells from damage duringthe cancer chemotherapy or radiotherapy. In a preferred embodiment, themethod is used to prevent baldness during cancer therapy, by applyingthe composition to the scalp. In another preferred embodiment, themethod is used to prevent gastrointestinal distress due to cancertherapy, by administering the composition orally. In yet anotherpreferred embodiment, the method is used to prevent skin rash andulceration at the site of irradiation by applying the composition to theskin.

In preferred embodiments of the foregoing aspects of the invention, thechemotherapeutic agent is one or a combination of agents selected fromthe group consisting of alkylating agents, antimetabolite inhibitors ofDNA synthesis, antitumor antibiotics, mitotic spindle poisons and vincaalkaloids. Examples include, but are not limited to, altretamine,asparaginase, bleomycin, busulfan, carboplatin, cisplatin, carmustine,chlorambucil, cladribine, cyclophosphamide, cytarabine, dacarbazine,dactinomycin, daunorubicin, doxorubicin, etoposide, floxuridine,fludarabine phosphate, fluorouracil, hydroxyurea, idarubicin,ifosfamide, lomustine, mechlorethamine, nitrogen mustard, melphalan,mercaptopurine, methotrexate, mitomycin, mitoxantrone, paclitaxel,pentostatin, pliamycin, procarbazine, streptozocin, teniposide,thioguanine, thiotepa, vinblastine and vincristine. The radiationtherapy is selected from the group consisting of x-rays, γ-rays,electron beams, photons, α-particles and neutrons.

In a preferred embodiment, the chemoprotective inducing agent is onethat induces phase I and phase II drug metabolizing enzymes. Such agentsare known in the art (e.g., Hayes et al., Biochem. Soc. Symp. 64,141-168, 2000) and include such classes of compounds as coumarins,lactones, diterpenes, dithiolethione flavones, indoles, isothiocyanates,organosulfides and phenols. Specific examples include, but are notlimited to, 3-tert-butyl-4-hydroxyanisole,2-tert-butyl-4-hydroxyanisole, 2-tert-butyl-1,4-dimethoxybenzene,2-tert-butylhydroquinone, 4-hydroxyanisole, ethoxyquin, α-angelicalactone, β-napthoflavone (β-NF), p-methoxyphenol, oltipraz,indole-3-carbinol, omeprazol, coumarin, cafestol, kahweol, quercitin,indole-3-acetonitrile, allyl isothiocyanate, benzyl isothiocyanate,eugenol, phenethyl isothiocyanate, sulphoraphane, allyl methyldisulfide, diallyl sulfide, butylated hydroxytoluene, ellagic acid andferulic acid.

According to another aspect of the invention, an assay is provided foridentifying chemoprotective inducing agents, as defined hereinbelow. Theassay comprises the steps of: (a) providing a cell transformed with aDNA construct comprising a reporter gene operably linked to a promoterand to one or more EpRE regulatory elements, (b) exposing the cell to atest compound being screened for possible utility as a chemoprotectiveinducing agent, and (c) measuring expression of the reporter gene, anincrease in the expression in the presence of the test compound, ascompared with the expression in the absence of the test compound, beingindicative that the test compound is a chemoprotective inducing agent. Akit is also provided in accordance with this aspect of the invention, tofacilitate performance of the assay.

According to another aspect of the invention, a method is provided forpreventing cancer caused by exposure of cells to environmentalcarcinogens. This method comprises providing as part of a regulardietary regime one or more chemoprotective inducing agents in an amounteffective to stimulate expression of cellular detoxifying enzymes,thereby protecting cells from the effects of the environmentalcarcinogens, upon exposure thereto.

Other features and advantages of the present invention will beunderstood from the drawings, detailed description and examples thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Effect of chemoprotective inducing agents on hair loss in ratpups treated with cytoxan. Chemoprotective agents were prepared fordelivery in a lipid droplet suspension or DMSO (Example 1) Upper inset:experimental protocol (Example 1); lower inset: histogram showing hairdensity in cytoxan-treated rat pups pre-treated with differentchemoprotective inducing agents; photographs (left to right, upper tolower): control (untreated with cytoxan or chemoprotective inducer);cytoxan treated; cytoxan treated and pre-treated with (1) BNF (threepanels), (2) Oltipraz (two panels), (3) BHA (one panel), (4) tBHQ (onepanel), (5) sulphoraphane (one panel), and (6) CG09 (two panels).

FIG. 2. Effect of chemoprotective inducing agents on hair loss in ratpups treated with cytoxan. Chemoprotective agents were prepared fordelivery in a propylene glycol:ethanol:water mixture of a type used fordelivery of Minoxidil (Example 1). Results demonstrate that minoxidilcarrier was not effective in delivery of chemoprotective inducers. Ratpups treated with CG09 or BNF in the minoxidil carrier suffered hairloss equivalent to that observed in cytoxan-treated animals notpre-treated with the chemoprotective inducer.

FIG. 3. Gene expression pattern of stress genes in rat pups treated withBNF and cytoxan. Rat pups were treated with either carrier alone(control), cytoxan, or BNF and at different time intervals skin sampleswere collected and cDNA samples prepared from MRNA extracted from thesamples. The radiolabeled cDNA synthesized was used to probe a ratstress gene cDNA expression array consisting of 207 stress-related genes(Clontech) according to the manufacturer's protocol.

FIG. 4. Histogram depicting the expression of exogenous Luciferase inrats treated with two liposomal formulations. Nonionic (NI) liposomes orNI+DOTAP were formulated to encapsulate 250 μg luciferase DNA and 250 μgβ-galactosidase DNA. Luciferase activity was measured at 0, 4, 8, 16 and24 hours after administration of the liposomal formulations.

FIG. 5. Histogram depicting the expression of exogenous β-galactosidaseactivity in rats treated with different liposomal formulations (Exanple2). Liposomes or other carriers were formulated to encapsulate 250 μgluciferase DNA and 250 μg β-galactosidase DNA. Luciferase activity wasmeasured at 0, 4, 8, 16 and 24 hours after administration of theformulations.

FIG. 6. Histogram showing expression of a series of genes in rats, whoseexpression in rat dermal cells is induced in the 1-6 (BNF1-BNF6) daysfollowing daily application of a βNF/nonionic liposome emulsion to theskin. Bars show, from left to right, control and BNF1-BNF6.

FIG. 7. Histogram showing expression of a series of genes in rats, whoseexpression in rat dermal cells is induced 5 days following dailyapplication of a βNF/nonionic liposome emulsion to the skin. Comparisonis made to gene expression following a single intraperitoneal injectionof cytoxan. From left to right: control, cytoxan, βNF.

FIG. 8. Construction of the GFP reporter plasmid. Fragments containingsingle or concatamerized 41 bp EpRE motifs and/or a TK promoter fragmentwere inserted into a multiple cloning site in the GFP vector.

FIG. 9. Basal and induced levels of GFP expression in HepG2 cell clonesstably carrying the indicated GFP reporter genes. Cells were treatedwith 90 mM tBHQ for 24 hr or DMSO (0.1% final concentration) as control.Cells carried the following expression genes: TK-GFP, 1×EpRE/TK-GFP,2×EpRE/TK-GFP, 4×EpRE/TK-GFP. GFP expression level was determined usinga fluorescence plate reader. Values are presented as the mean±S.D.

FIG. 10. Correlation between the number of cells plated and DNA contentof the well based upon EtBr or GFP fluorescence. Intensity offluorescence per well was determined as described in Example 4. Valuesare presented as the means±S.D. for three determinations.

FIG. 11. Time and dose-dependency of GFP expression in tBHQ-treatedHepG2 cells. Cells carrying an integrated 4×EpRE/TK reporter constructwere treated (A) with 90 μM tBHQ for the indicated times, or (B) withthe indicated TBHQ concentration for 24 hr. GFP expression level wasdetermined using a fluorescence plate reader. Values are presented asthe means±S.D. for three determinations.

FIG. 12. Dose-dependent induction of GFP expression by knownchemopreventive inducer molecules. HepG2 cells were plated in 96-wellmicrotiter plates (5×10⁴ cells/well) for 24 hr and then treated with theindicated chemicals as described in Materials and Methods. Data areexpressed as the means±SD of three parallel cultures. The relativefluorescence intensity ratio was calculated using a value of 1 for thecontrol dish.

FIG. 13. A typical 3D graph from the screening test which represents thefluorescence data captured from the test plate and analyzed by computerto illustrate the induction level for positive controls (tBHQ, lane 1,and β-NF, lane 12) and each test compound. Compound CG09 is shown inlane 6.

FIG. 14. Level of induced GFP expression from both known inducers and ahit compound (09G06) from the chemical library screening. Data arepresented as the mean±SD of three determinations.

FIG. 15. Structures of certain molecules from ChemBridge library, whichdisplay chemoprotective inducing activity. Compound CG09 is Structure 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides compositions and methods for protectingnon-cancerous, rapidly dividing cells in a patient's body from the toxiceffects of chemotherapeutic agents or radiotherapy administered to thepatient. In particular, the compositions and methods of the inventionare designed for protecting epithelial cells. Most particularly, thetargets are epithelial cells lining hair follicles and epithelial cellsof the gastrointestinal tract.

Further applications of this invention are also anticipated at othercell sites that are affected when a patient is administered chemotherapyor radiotherapy. For instance, several skin pathologies have beenobserved in patients who receive intense regimens of chemotherapy and/orradiation therapy. These typically occur on the skin within the field ofradiation therapy that is targeted to a tumor in an underlying organ. Asone example, chest skin lesions often occur in patients irradiated forlung cancer. Another example is the occurrence of mucositis; i.e.,development of mouth sores, in patients undergoing radiation therapy ofthe head and neck. Additionally, a phenomenon called “radiation recall”sometimes arises in patients previously irradiated without incident,wherein skin lesions occur when the patient is subsequently treated withcytoxan.

The skin lesions are generally variations of dermatitis; they canconsist of dermis breakdown and ulceration (including the mouth soresmentioned above), generalized dermal rash, or scattered red lesions in arecurrently irradiated skin field. Formation of these cancertherapy-induced lesions is consistent with the high level of celldivision that is always occurring within the epidermal layer of normalskin. The compositions of the present invention are contemplated to beof great utility in treating these skin fields that are at risk fromrecurrent radiation, as well as possible coincident systemicchemotherapy.

As illustrated in FIG. 3, the expression of a very large number ofstress response genes is activated following exposure of the skin to anyof several chemoprotective inducing agents. This group of activatedgenes encodes proteins directly involved in the phase II detoxificationof drugs and reactive oxygen species, such as several GST isoforms,catalase and quinone reductase, to name a few, as well as proteinsresponsible for the export of drug molecules from cells, such as mdr-2,MRP, and the like. Also included are DNA repair enzymes. Because of thisbroad, up-regulated response, the inventors anticipate a resistancephenotype to a wide variety of drugs that includes alkylating molecules,but extends to many other cancer chemotherapy drug groups, such asantimetabolites, topoisomerase inhibitors, microtubule inhibitors,mitotic spindle poisons, antitumor antibiotics and vinca alkaloids. Evenif the drug is not directly metabolized by one of the stress responsegene products, it is still likely to be more rapidly exported from thecell by one or more of the up-regulated membrane drug export pumps.Examples of chemotherapeutic agents against which resistance in normalcells can be induced include, but are not limited to: altretamine,asparaginase, bleomycin, busulfan, carboplatin, cisplatin, carmustine,chlorambucil, cladribine, cyclophosphamide, cytarabine, dacarbazine,dactinomycin, daunorubicin, doxorubicin, etoposide, floxuridine,fludarabine phosphate, fluorouracil, hydroxyurea, idarubicin,ifosfamide, lomustine, mechlorethamine, nitrogen mustard, melphalan,mercaptopurine, methotrexate, mitomycin, mitoxantrone, paclitaxel,pentostatin, pliamycin, procarbazine, streptozocin, teniposide,thioguanine, thiotepa, vinblastine and vincristine.

Thus, the present invention makes use of the cell's ability to producebiological molecules that act as detoxifying agents for the cell. Asused herein, the term “detoxifying agent” refers to an agent that,directly or indirectly, is capable of reducing or eliminating the toxiceffect of one or more chemotherapeutic agents or of radiotherapy.Several categories of detoxifying agents are produced in cells. Onecategory of agents acts by modifying the toxic compound to either reduceits toxicity or render it amenable to subsequent excretion from thecell. For example, most of the alkylating agents used in chemotherapyare lipophilic electrophiles that possess a major hydrophobic region.The absence of a direct exporting mechanism to remove these agents fromcells results in a gradual intracellular accumulation of thesehydrophobic electrophiles. Glutathione-S-transferases (GSTs) arewell-known for their ability to inactivate a variety of antineoplasticalkylating drugs. GSTs are one group of enzymes that have an importantrole in protecting cells from the damage caused by electrophiliccompounds. Another agent that acts by converting the chemotherapeuticagent to a less toxic form or a form that is more easily removed fromthe cell is aldehyde dehydrogenase. This molecule has been shown to beassociated with increased resistance of cells to the effects ofalkylating agents, including carboplatin and oxazaphosphorines, such ascyclophosphamide and 4-hydroperoxycyclophosphamide (Tanner et al., Gyn.Oncol. 65: 54-62, 1997; Bunting & Townsend, J. Biol. Chem. 271:11884-11890, 1996). Aldehyde dehydrogenase catalyzes the oxidation ofaldophosphamide, a key intermediate in the activation pathway ofoxazaphosphorines, thereby detoxifying these agents (Sreerama & Sladek,Drug Metabolism and Disposition 23: 1080-1084, 1995).

Another category of detoxifying agents acts by facilitating transport oftoxic agents (either modified for export as described above, orunmodified) out of cells. For instance, certain ATP-binding cassette(ABC) transporters have been identified in a wide variety of organisms,including mammals, that appear to act in this manner. Two well studiedgroups of ABC transporters, encoded by mdr and mrp genes, respectively,are associated with the multi-drug resistance phenomenon observed inmammalian tumor cells. The mdr genes encode a family of P-glycoproteinsthat mediate the energy-dependent efflux of certain lipophilic drugs(e.g., adriamycin, vinblastine, taxol) from cells. The mrp genes encodea family of transporters whose specificity overlaps that of the mdr geneproduct, but which also mediates the extrusion of a variety of organiccompounds after their conjugation with glutathione.

It has been discovered in accordance with the present invention thatelevation of one or more of these detoxifying agents in epithelial cellsserves to protect the cells against the toxic effect of one or more ofthe chemotherapeutic agents enumerated above, as well as protecting themfrom damage during the course of radiation therapy. Thus, the presentinvention in its most basic aspect is drawn to delivering or otherwiseincreasing the production of such agents in epithelial cells before orduring the early course of chemotherapy and/or radiotherapy, to protectthe cells from cancer therapy-associated damage.

It should be noted, however, that most of the detoxifying agents listedabove are enzymes. Delivery of polypeptides or genes encoding thosepolypeptides to a selected cell population, such that an effectiveamount of the detoxifying enzymes are present in those cells, isdifficult and unpredictable. Accordingly, the present invention relieson inducing increased production of those enzymes in target cells byadministration of small molecules that are known, or have beendiscovered, to induce increased production of one or more cellulardetoxifying agents. These molecules are referred to herein as“chemoprotective inducers” or “chemoprotective inducing agents” ormolecules. Thus, as defined herein, a “chemoprotective inducer” or“chemoprotective inducing agent” is an agent that, upon delivery to acell, induces or increases production of the cell's endogenousdetoxifying agents, as defined above.

It has been discovered in accordance with the present invention thatchemoprotective inducers can be efficiently delivered to target cellpopulations, where they are capable of entering the cells and inducingor increasing production of one or more detoxifying enzymes by a varietyof means, e.g., inducing increased expression of genes encoding theenzymes. The resultant benefit is the alleviation of symptoms associatedwith chemotherapy or radiotherapy; most notably, hair loss andgastrointestinal distress, as will be discussed in greater detail below.

The compositions of the invention comprise one or more chemoprotectiveinducers, which exert a detoxifying effect on one or more of thechemotherapeutic agents described above by inducing production ofendogenous detoxifying molecules, and a delivery vehicle for deliveringthe chemoprotective inducers to the cells and tissues targeted forprotection.

Chemoprotective inducing agent. For purposes of the present invention, a“chemoprotective inducer” may be any agent which, upon delivery to anepithelial cell, induces or increases production of a detoxifyingmolecule (as defined above) within the cell. Without intending to belimited by any explanation as to mechanism of action, the experimentalresults set forth herein suggest that these chemoprotective inducers areeffective because they provide a mild oxidative stress that stimulatescells to produce a battery of stress-response molecules, such that thosemolecules are already increased in presence or activity when the moresevere stress of chemotherapy or radiotherapy is imposed. This mechanismis sometimes referred to herein as “metabolic vaccination”, due to itsfunctional similarity to the vaccination process.

A second group of compounds, either alone or combined with the abovecompounds, to be included as “chemoprotective inducers” includescompounds that are functional ligands of the aryl hydrocarbon (Ah)receptor. In some cases, the hallmark induced expression of thecytochrome P45 1A1 gene resulting from an activated Ah receptor mayprovide a phase I metabolic step in detoxifying a drug, which will befollowed by conjugation of the metabolite by one or more of the inducedGSTs that are an integral part of the stress response gene battery. Inessence, then, these compounds provide the opportunity for the cell toexert a metabolic “one-two punch” to remove a toxic drug from the cell.Examples of Ah receptor ligands that could be used in this capacityinclude, but are not limited to, indole-3-carbinol from cruciferousvegetables, and omerprazole (Jellink et al., Biochem. Pharmacol. 45:1129-1136, 1993; Dzeletovic et al., J. Biol. Chem. 272: 12705-12713,1997). Other suitable Ah ligands are known in the art.

Many chemoprotective inducing agents known in the art are suitable foruse in the present invention (e.g., DeLong et al., Cancer Res. 45:546-551, 1985; Ioannou et al., Cancer Res. 42: 1199-1204, 1982; Chung etal., Cancer Res. 46: 165-168, 1986; Wattenberg et al., Cancer Res. 40:2820-2823, 1980; and Kensler et al.; Cancer Res. 46: 3924-3931, 1986).Examples include, but are not limited to: 3-tert-butyl-4-hydroxyanisole(3-BHA), 2-tert-butyl-4-hydroxyanisole (2-BHA),2-tert-butyl-1,4-dimethoxybenzene(methyl-BHA),2-tert-butylhydroxyquinone (t-BHQ), 4-hdroxyanisole, ethoxyquin,α-angelica lactone, β-napthoflavone (β-NF), p-methoxyphenol andoltipraz. In addition to these, using methods disclosed herein inaccordance with the invention, other chemoprotective inducers have beenidentified, including the molecules shown in FIG. 15, identified from asmall molecule library from ChemBridge Corporation (San Diego, Calif.).As shown in FIG. 15, the most potent chemoprotective inducing agentidentified thus far is CG09 from the Chembridge library (Structure 1 inFIG. 15).

Some of the molecules listed above (e.g, BHA) are used as chemicalantioxidants in the food industry. However, as appreciated in thisinvention, their effect is as oxidants upon metabolism in the body. Forinstance, when BHA is administered to mammals, it is metabolized toyield tert-butylhydroquinone (t-BHQ) as a primary metabolite. Like mosthydroquinones in cell systems, t-BHQ spontaneously undergoes cyclicconversion between the quinone and hydroquinone forms, i.e., redoxcycling in the cells. A side-product of redox cycling is the formationof one or more forms of oxygen free radical. The cells sense theseoxygen free radicals as an environmental stress, which triggersexpression of stress-response genes. It is in this manner that chemicalantioxidants such as BHA may become effective oxidants in the cell, soas to act as chemoprotective inducers as defined herein.

Delivery vehicle. The compositions of the invention also comprise adelivery vehicle. The main function of the delivery vehicle is to carrythe chemoprotective inducer(s) to the cell population or tissue targetedfor protection from the chemotherapeutic agents.

Delivery of organic and biological substances via the skin using anoninvasive carrier system has many attractions, including patientacceptability due to the noninvasiveness of the procedure and avoidanceof gastrointestinal disturbances and first-pass metabolism of thedelivered molecule. However, the major problem in dermal delivery is thelow penetration rate of most substances through the barrier of the skinstratum corneum. The skin consists of two layers, dermis and epidermis.The dermis consists of connective tissue, nerves, blood and lymphvessels, hair follicles, sebaceous and sweat glands. Epidermis consistsof cells in several stages of differentiation; during thisdifferentiation the cells migrate from the basal layer to the surfaceand cornify to form stratum corneum. The lipid matrix of the stratumcorneum is formed of double-layered lipid membranes composed ofcholesterol, free fatty acids and ceramides. Although the stratumcorneum is considered to be the main barrier to percutaneous absorption,it is also regarded as the main pathway for penetration. Thereforecompounds that loosen or fluidize the lipid matrix of the stratumcorneum may enhance the permeation of substances through the skin. Thisis usually achieved by utilizing carrier molecules like albuminconjugates, lecithins, glycoproteins, polysaccharides and liposomes.

Among these choices, liposomal formulations offer several advantagesover more conventional formulations. The major advantages are: (1)reduced serious side effects and incompatability from undesirably highsystemic absorption; (2) significantly enhanced accumulation of thedelivered substance at the site of administration due to highcompatability of liposomes with stratum corneum; (3) ready incorporationof a wide variety of hydrophilic and hydrophobic molecules into theskin; (4) protection of the entrapped compound from metabolicdegradation; and (5) close resemblance to the natural membrane structureand their associated biocompatibility and biodegradability.

Liposomes may be defined as spherical concentric fluid mosaics made fromhighly precise self-assembly of phospholipid molecules which are formedwhen phospholipids are dispersed in aqueous medium. When lipids areplaced in aqueous medium, the hydrophilic interaction of the lipid headgroups with water results in the formation of multilamellar andunilamellar systems or vesicles which resemble biological membranes inthe form of a spherical shell. These basic liposomes are sometimesreferred to as “conventional liposomes.” Several other types ofliposomal preparations exist, including (1) sterically stabilizedliposomes, which are surface coated with an inert hydrophilic polymer,such as polyethylene glycol; (2) targeted liposomes, to which areattached targeting ligands, such as antibodies or fragments thereof,lectins, oligosaccharides or peptides (as discussed below, choleratoxinB (CTB) is used to target liposomes to the gastrointestinal epithelium);and (3) reactive or “polymorphic” liposomes, which change their phaseand structure in response to a particular interaction (this groupincludes liposomes sensitive to ions (pH, cations), heat and light,among other stimuli. For a review of the different types of liposomeslisted above, see Chapter 6 of D. Lasic, Liposomes in Gene Delivery, CRCPress, 1994.

In order to achieve efficient delivery of a chemoprotective moleculeinto the skin, various formulations of liposomes (phospholipid-basedvesicles, cationic liposomes, nonionic liposomes, non ionic/cationicliposomes, pegylated liposomes, PINC polymer, and propylene glycol andethanol mixture (commonly used vehicle for administering minoxidil), andnonionic liposome/propylene glycol and ethanol mixtures were tested (seeExamples). It was determined that nonionic liposomes or a mixture ofnonionic liposomes and propylene glycol/ethanol are the most effectivetransdermal carriers.

Reactive liposomes may be preferred for other embodiments of the presentinvention. Inclusion of cationic amphiphiles as a minor component ofliposomes facilitates the association with negatively charged solutes,the rapid binding of liposomes to the cell surface, and the cellularuptake of liposomes. pH-sensitive liposomes have been developed toimprove the efficiency of the cytoplasmic delivery of antitumor drugs,proteins, and nucleic acids. Most pH-sensitive liposomes have beenprepared using phosphatidylethanolamine (PE). PE alone does not formliposomes and is prone to form the inverted hexagonal phase (H_(II)).However, liposomes can be prepared by adding anotherbilayer-stabilizing, amphiphilic lipid component to PE. Titratableamphiphiles having a carboxyl group have been used as a component forthe preparation of pH-sensitive liposomes. Because the ability tostabilize a bilayer membrane by these titratable amphiphiles decreasesunder acidic conditions, destabilization results in the fusion of theliposomes. pH-sensitive liposomes are stable at physiological pH, andare internalized by cells through an endocytic pathway, which exposesthe liposomes to an acidic pH. Liposomes within the endosome aredestabilized and possibly fuse with the endosome membrane, resulting inrelease of their contents into the cytoplasm without degradation bylysosomal enzymes.

In other embodiments of the invention, sterically stabilized, inertliposomes are particularly suitable. In still other embodiments,targeted liposomes may be used to advantage.

In other embodiments of the invention, particularly for administrationof chemoprotective inducing agents to the epidermis, lipid-based“creams” are particularly well suited. Creams are generally formulatedto include water, alcohol, propylene glycol, sodium lauryl sulfate andwhite wax. In alternative formulations, they include water, alcohol,glycerol, phosphatidyl choline, lysophosphatidyl choline andtriglycerides.

Other delivery vehicles are also suitable for use in the presentinvention, particularly for administration of detoxifying agents to thegastrointestinal lumen. Nonlimiting examples include: (1) oils such asvegetable oils or fish oils (which can be encapsulated into standard gelcapsules); and (2) emulsions prepared by dispersing polyoxyethyleneethers, e.g., 10-stearyl ether (Brij 76) in aqueous buffer.

Other examples of delivery vehicles suitable for the GI lumen includebiodegradable microparticles (0.1-10 μM diameter) of polylacticpolyglycolic acid, which have been used to deliver proteins to Caco-2cells as an in vitro model system for gastrointestinal uptake via oraldrug delivery (Desai et al., Pharm. Res. 14: 1568-1573, 1997). Othershave shown significant uptake of proteins carried by polystyreneparticles into cells lining the small intestine of the rat (Hillery etal., J. Drug Targeting 2: 151-156, 1994). Indeed, delivery ofprotein-containing microparticles has been reported from the GI lumenall the way to the submucosal vasculature (Aphramaian et al., Biol. Cell61: 69-76, 1987). Therefore, such polymeric microparticles are quitesuitable for oral delivery of chemoprotective inducing agents togastrointestinal epithelial cells, which are found on the surface of theGI lumen.

Administration of pharmaceutical preparations comprising chemoprotectiveinducers. Depending on the cell population or tissue targeted forprotection, the following modes of administration of the compositions ofthe invention are contemplated: topical, oral, nasal, ophthalmic,rectal, vaginal, subcutaneous, intraperitoneal and intravenous. Becausetargeted delivery is contemplated, certain of these modes ofadministration are most suitable for targeted delivery vehicles (e.g.,CTB- or antibody-studded liposomes).

The compositions of the present invention are generally administered toa patient as a pharmaceutical preparation. The term “patient” as usedherein refers to human or animal subjects (animals being particularlyuseful as models for clinical efficacy of a particular composition).Selection of a suitable pharmaceutical preparation depends upon themethod of administration chosen, and may be made according to protocolswell known to medicinal chemists.

The pharmaceutical preparation comprising the compositions of theinvention are conveniently formulated for administration with aacceptable medium such as water, buffered saline, ethanol, polyol (forexample, glycerol, propylene glycol, liquid polyethylene glycol and thelike), dimethyl sulfoxide (DMSO), oils, detergents, suspending agents orsuitable mixtures thereof. The concentration of a particular compositionin the chosen medium will depend on the hydrophobic or hydrophilicnature of the medium, in combination with the specific properties of thedelivery vehicle and active agents disposed therein. Solubility limitsmay be easily determined by one skilled in the art.

As used herein, “biologically acceptable medium” includes any and allsolvents, dispersion media and the like which may be appropriate for thedesired route of administration of the pharmaceutical preparation, asexemplified in the preceding paragraph. The use of such media forpharmaceutically active substances is known in the art. Except insofaras any conventional media or agent is incompatible with the compositionsto be administered, its use in the pharmaceutical preparation iscontemplated.

The pharmaceutical preparation is formulated in dosage unit form forease of administration and uniformity of dosage. Dosage unit form, asused herein, refers to a physically discrete unit of the pharmaceuticalpreparation appropriate for the patient undergoing treatment. Eachdosage should contain a quantity of the chemoprotective inducingagent(s) calculated to produce the desired protective effect inassociation with the selected pharmaceutical carrier. Procedures fordetermining the appropriate dosage unit are well known to those skilledin the art.

Dosage units may be proportionately increased or decreased based on theweight of the patient. Appropriate concentrations for achievingprotection of a target cell population or tissue from the toxic effectof a particular chemotherapeutic agent may be determined by dosageconcentration curve calculations, as known in the art.

As one example, for topical applications, the chemoprotective inducersmay be used at concentrations ranging from 5-100 mM in an appropriatecarrier (e.g., liposome emulsion) applied to the scalp or other dermalsite. This dosage is arrived at from results of experiments using arodent model (see Examples 1-3), and the range of dosages is a functionof results obtained from experiments using several different moleculesthat ranged in dose effectiveness. The volume of material applied to theskin ranges by size of surface area to be covered; e.g., scalp treatmentfor young children requiring 3-5 ml, the amount being increased inadults to 10-20 ml per application.

As another example, for gastrointestinal, administration, the oral doseof the chemoprotective inducer in an appropriate medium (e.g., liposomeemulsion) is normalized to the lumenal surface area of the stomach andduodenum. This would assume that the patient consumes the material on anempty stomach upon rising in the morning.

Regimens for administration of pharmaceutical preparations. Thepharmaceutical preparation comprising the compositions of the inventionmay be administered at appropriate intervals, before, during, or after aregimen of chemotherapy and/or radiotherapy. The appropriate interval ina particular case would normally depend on the nature of thechemotherapy or radiotherapy and the cell population targeted forprotection.

For instance, for prevention of chemotherapy-induced alopecia, liposomesor other delivery vehicles containing chemoprotective inducing agentscan be formulated to be delivered, e.g., as a topical cream, to thescalp of a patient prior to scheduled administration of chemotherapy. Byprotecting the epithelial cells that line the exposed surface of hairfollicles from the chemotherapy drug, the loss of hair commonlyassociated with cancer chemotherapy can be prevented. As described ingreater detail in the examples, the topical formulation preferably isinitiated 1-5 days prior to chemotherapy, to ensure that the induceddetoxifying gene products are fully activated in the follicularepithelial cells when the chemotherapy is administered. The formulationmay then continue to be applied during the course of chemotherapy.

For protection of the gastrointestinal epithelium, chemoprotectiveinducers are formulated to be delivered by mouth to a patient prior toscheduled administration of chemotherapy. Administration of theprotective formulation in the 1-5 days prior to the infusion of thechemotherapeutic agent thus confers protection to susceptible epithelialcells. For example, the patient would be instructed to consume a “shake”containing the chemoprotective inducer/liposome emulsion beforebreakfast in the morning, in the 1-5 days preceding chemotherapy. As aresult, levels of the stress response gene products would be present attheir induced maximum at the time when the chemotherapy drugs permeatethe GI lumenal epithelium.

Identification of novel chemoprotective inducing agents. As discussedabove, a variety of molecules are known to induce stress response genesin cells, thereby providing the chemoprotective inducing effect utilizedin the present invention. However, it would be an advance in the art todevise a simple method for identifying new chemoprotective inducers withequivalent or superior activity. Hence, the present invention alsoprovides a rapid and simple assay system for screening candidatemolecules for their ability to induce or increase the production oractivity of one or more stress response molecules capable of detoxifyinga cell of damaging chemotherapeutic agents or biproducts of radiationtherapy. The method is described in detail in Example 4. The assay isbased on the demonstration that the electrophile responsive element(EpRE) mediates the induced expression of phase II detoxifying enzymesand oxidative stress proteins, which constitutes an important mechanismof cellular protection from a variety of environmental agents (Wassermanet al., Proc. Natl. Acad. Sci. USA 94: 5361-5366, 1997). The assayutilizes a DNA construct comprising a reporter gene operably linked to apromoter, adjacent to which are inserted one or more EpRE regulatoryelements. Cells are transformed with the DNA construct, and clonesselected which display low presence or activity of the expressedreporter gene product (negative control), with inducible high presenceor activity of the reporter gene product upon exposure of the cells to aknown inducer of phase II detoxifying enzymes (positive control). Thecells are then exposed to candidate test compounds, and the level ofexpression of the reporter gene is measured. This assay can be assembledin a multiple well system for the simultaneous testing of many testcompounds.

In a preferred embodiment of the invention, the reporter gene encodes agreen fluorescent protein, as described in Example 4, under control of athymidine kinase promoter and a concatemer of EpRE regulatory elements.

Also provided in accordance with the invention is a kit to facilitatepractice of the screening assay. The kit comprises the DNA construct andinstructions for carrying out the assay. In addition, the kit optionallymay comprise a cultured cell suitable for transformation, reagents touse as controls in the assay, reagents for detecting the amount ofexpression of the reporter gene, and other various culture media orbiochemical reagents, as appropriate.

Use of chemoprotective inducers to prevent cancer. Though the etiologyof cancer is not thoroughly understood, it is well known that certainchemicals or environmental agents act as mutagens and carcinogens. Forthis reason, the present invention also contemplates the use of thechemoprotective inducer formulations as a cancer preventative.Prophylactic consumption of these agents as part of a daily diet regimewill result in chronic induced expression of chemoprotective genes in ahost of normal organs, such as stomach and intestines, as well as non-GItissues such as breast. The chronic increase in detoxifying cellularproteins will better enable those cells to detoxify chemical carcinogensencountered in everyday life, such carcinogens commonly arising fromsmoking and food by-products.

The following examples are provided to illustrate the invention. Theyare not intended to limit the invention in any way.

EXAMPLE 1 Prevention of Chemotherapy-Induced Alopecia by TopicalApplication of Molecules that Induce Expression of Chemoprotective GeneProducts

The inventors postulated that drug induced alopecia could to a largeextent be successfully prevented by selective protection of hairfollicles by expressing chemoprotective gene products such as GSTs, MRP,MDR, ALDH3 and the like, that are known to protect cells againstcytotoxicity. Combined, increased expression of MRP and GST P1 has beenfound to confer high level resistance to the cytotoxicities ofanticancer drugs (Morrow et al, 1998); however, expression of either MRPor GST alone was found to be less successful as these gene products workin synergy to protect cancerous cells against cytotoxicity by theircoordinated action in the removal of the anticancer drugs from cells.

The experiments set forth in this example were designed with the idea ofoverexpressing these protective genes in hair follicle cells bydelivering molecules that are known to induce the expression of theabove mentioned chemoprotective genes. Alopecia was induced in 7 day oldrat pups by administering cytoxan (FIG. 1 inset). Before and duringcytoxan administration, the rats were treated with chemoprotectivemolecules using nonionic liposomes as the vehicle for entry into thehair follicles, and the efficacy of each of the chemoprotectants in theprevention of alopecia was determined.

Materials and Methods:

Induction of alopecia by cytoxan (CTX). Lactating Sprague Dawley ratswith 12 pups per mother were purchased from Harlan Sprague Dawley. Toproduce CTX induced alopecia, several concentrations (35, 40 45 μg/gmbody weight) of CTX in water were injected i.p. in to 7 day old pups.Seven days after CTX treatment the pups were examined to determine thedegree of hair loss. The pups were gently brushed on the back to removethe loose hair sticking onto the skin and photographed. The density ofhair on the pups was then determined. 100% hair density represents thatfound on the untreated control pups while 0% represented pups with totalhair loss. It was observed that 40 μg/gm of CTX was sufficient to induce100% hair loss on 7 day old pups and this concentration was used insubsequent experiments.

Treatment with chemoprotectants; preparation of nonionic liposomes asthe vehicle for delivery. The nonionic liposome preparations containedglyceryl dilaurate (GDL), Cholesterol, Polyoxyethylene-10-stearyl ether(POE-10) at a weight percentage ratio of 58:15:27. The lipid mixturealso contained 1% α-tocopherol. Appropriate amounts of the lipids weremixed (100 mg/ml total lipid) and melted at 70° C. in a sterilepolystyrene tube. The lipid mixture was drawn into a sterile syringe. Asecond syringe containing sterile PBS was preheated to 70° C. andconnected via a 2-way stopcock to the lipid phase syringe. The aqueousphase was then slowly injected into the lipid phase syringe. The mixturewas rapidly passed back and forth between the two syringes while beingcooled under running cold tap water until the mixture reached roomtemperature. The final preparation was examined under a microscope toassure integrity and quality of the liposomes. Immediately before use,the liposomes were sonicated at RT for 2 min and mixed with an equalvolume of the chemoprotectant in a suitable solvent (typically, DMSO)and incubated at RT for 45 min.

Several nonionic liposomal preparations were prepared containing thefollowing chemoprotectants:

-   -   5 mM B-NF    -   10 mM B-NF    -   15 mM B-NF    -   5 mM CG09    -   10 mM CG09    -   15 mM CG09    -   20 mM CG09    -   25 mm BHA    -   50 mM BHA    -   25 mM tBHQ    -   50 mM tBHQ    -   5 mM sulphoraphane    -   10 mM sulphoraphane    -   15 mM oltipraz    -   20 mM oltipraz        The liposome formulations were applied using a pipetman onto a 1        square cm area of the dorsal back of 7 day old rat pups skin        starting from day—2 of the experiment. On day 0 of the        experiment, the animals were injected with 40 μg/gm CTX. The        application of the liposome preparations continued until day 6        of the experiment. The control animals received only the empty        liposomes. On day 7 of the experiment, the animals were scored        to determine the degree of alopecia. The pups were gently rubbed        on their backs to remove the loose hair and were photographed.        FIG. 1 illustrates the effect of the chemoprotective molecules        on the prevention of hair loss.        Results:

Among the known chemoprotective compounds, B-NF had an 80% protectiveeffect followed by BHA (60%), Oltipraz(50%), tBHQ (10%) andsulphoraphane (5%). The newly discovered compound CG09 showed thehighest level of protection at ˜97% (FIG. 1 inset). The hair texture wasalso found to be comparable to that of untreated rat pups. It wasobserved that, when the chemoprotective molecules were delivered usingDMSO as the carrier, although the pups retained their hair after CTXtreatment, their skin was rough and scaly. The minoxidil carrier, apropylene glycol:ethanol:water mixture, failed to work as an effectivecarrier for these chemoprotective molecules. Alopecia in the pupstreated with B-NF or CG09 in the minoxidil vehicle was as severe as theuntreated CTX-treated rat pups (FIG. 2).

EXAMPLE 2 Effect of Small Molecule Inducers of Chemoprotective Genes onChemoprotective Gene Expression in Skin

To elucidate the basic mechanism underlying this protective effect ofB-NF and CG09, we studied the expression levels of chemoprotective genessuch as GSTs, MDR, MRP and ALDH3, under the same topical treatmentconditions as described in the previous example.

In brief, rat pups were treated with either CTX or B-NF and at differenttime intervals skin samples were collected and total RNA was extractedfrom them. The RNA was reverse transcribed to form the respective cDNAsin the presence of ³²P dATP using primers specific for stress-relatedgenes. The radiolabeled cDNA synthesized was used to probe a rat stressgene cDNA expression array consisting of 207 stress-related genes(Clontech) according to the manufacturer's protocol. The hybridizedmembrane was exposed to a phosphorimager screen and the image obtainedwas aligned with an orientation grid to identify the genes that areexpressed. Images from control, CTX-treated and B-NF-treated animalswere compared to determine the changes, if any, in the expressionpattern of chemoprotective genes under these experimental conditions.

FIG. 3 depicts the expression pattern of stress genes in rat pupstreated with B-NF and cytoxan. Topical administration of 15 mM B-NF torat pups for 5 days resulted in a significant increase in the expressionlevel for GST-PI, GST-Mu2, GST-Ya, and GST (rat homolog of human) whencompared to rat pups treated with cytoxan. FIG. 6 shows a series ofgenes whose expression in rat dermal cells, the majority of which arefollicular cells, is induced in the 1-6 days (β-NF1-β-NF6, plateauing onday 5) following daily application of the βNF/nonionic liposome emulsionto the rat pup's skin. Noteworthy points from the graph: (1) β-NF orCG09 were applied only on the day before cytoxan, but nevertheless, asubstantial protective effect was achieved; (2) the data provide astrong argument for starting the topical scalp treatment on day—5 withcytoxan administered on day 0, and then continuing topical treatmentthrough several days post cytoxan to enable cytoxan to be cleared fromthe patient's body; (3) the list of genes whose expression is induced(i.e., the names below the vertical bars) makes it clear why thetoxicity of cytoxan is nearly eliminated in the follicular cells. Thesegenes, several GSTs and aldehyde-dehydrogenase, are known to metabolizeand detoxify cytoxan and other alkylating drugs. The elevation of mdr-2gene, expression strongly suggests that a resistance or protectionphenotype in the follicular cells will be displayed when the animals aretreated with adriamycin, cytosine arabinoside and other drugs that areknown to induce alopecia and which are also known to be substrates forthe mdr-2 membrane efflux pump.

FIG. 7 shows the stress-response genes induced in dermal tissue on thefifth day of β-NF treatment (only) or on the fifth day followingsystemic administration of cytoxan (only). Systemic cytoxanadministration induces a subset of stress response genes in dermalcells. Unfortunately, cytoxan is long cleared and its damage done beforethe cytoxan-induced stress response genes are significantly expressed.Accordingly, the present invention utilizes the “molecular vaccination”technique of applying a more moderate stress inducer, such as β-NF, 1-5days prior to the administration of the chemotherapeutic agent, so thatexpression and detoxification activity of these enzymes is at a peakwhen the chemotherapeutic agent is delivered.

EXAMPLE 3 Identification of Carriers for Delivery of ChemoprotectiveGene Inducers to Epithelial Cells

In order to achieve efficient delivery of a chemoprotective moleculeinto the skin, studies were conducted using various formulations ofliposomes (phospholipid-based vesicles, cationic liposomes, nonionicliposomes, non ionic/cationic liposomes, pegylated liposomes, PINCpolymer, and propylene glycol and ethanol mixture (commonly used vehiclefor administering minoxidil). First, these formulations were used toentrap reporter genes such as those encoding the marker proteinsLuciferase or β-galactosidase, or a fluorescent probe (Nile Red), andtheir delivery was tracked in the target tissue by the functional assayof the marker proteins delivered or fluorescence emission in the case ofNile Red. The liposomes were prepared as set forth below.

Phospholipid based vesicles. The preparation contained the followinglipid mixtures in a 1:0.5:0.1 molar ratio:

-   -   1. DSPC: Cholesterol: DOTAP    -   2. DOPE: Cholesterol: DSPC    -   3. DOPE-2000: Cholesterol: DSPC        The lipids were dissolved in chloroform and evaporated in a        rotoevaporater at 50° C. The dried lipid film was hydrated with        HEPES buffer containing DNA (β-gal or Luciferase) or one mg of        Nile Red at RT for 30 min. The resulting suspension was        subjected to five cycles of freezing and thawing. The final        suspension was passed through 0.22 μm filter seven times. The        vesicles were stored at 4° C.

Nonionic liposomes. The nonionic liposomre preparations containedglyceryl dilaurate (GDL), cholesterol, polyoxyethylene-10-stearyl ether(POE-10) at a weight percentage ratio of 58:15:27. The lipid mixturealso contained 1% α-tocopherol. Appropriate amounts of the lipids weremixed (100 mg total lipid) and melted at 70° C. in a sterile polystyrenetube. The lipid mixture was drawn into a sterile syringe. A secondsyringe containing sterile PBS was preheated to 70° C. and connected viaa 2-way stopcock to the lipid phase syringe. The aqueous phase was thenslowly injected into the lipid phase syringe. The mixture was rapidlypassed back and forth between the two syringes while being cooled underrunning cold tap water until the mixture reached room temperature. Thefinal preparation was examined under a microscope to assure integrityand quality of the liposomes. Immediately before use, the liposomepreparation was sonicated for 2 min at RT and an equal volume ofreporter DNA (250 μg) was added and incubated at RT for an hour.

Nonionic/Cationic liposomes. The nonionic/cationic preparationscontained GDL, POE—10, cholesterol, DOTAP (1,2dioleyloxy-3(trimethylammonio) propane at a weight percent ratio of50:23:15:12 in a 100 mg/ml preparation. Appropriate amounts of thelipids were mixed and melted in a polystyrene tube at 70° C. and drawninto a syringe preheated to 70° C. A second syringe containing sterilePBS was preheated to 70° C. and connected to the lipid phase syringe viaa 2-way stopcock. The aqueous phase was slowly injected into the lipidphase syringe. The mixture was rapidly passed back and forth between thetwo syringes while being cooled under cold tap water until the mixturereached room temperature. Immediately before use, the liposomalsuspension was sonicated for 2 min at RT and an equal volume of (DNA 250μg) and nonionic/cationic liposomes were mixed and incubated at RT for 1hour.

PINC (Protective, Interactive and Non Condensing) polymers. Formulationswere made by mixing 70% PVP, 30% Vinyl Acetate and 250 μg plasmid DNA in0.9% NaCl and incubating at RT for 15 min.

PG (propylene glycol): Ethanol—plasmid DNA complex (Minoxidil vehicle).250 μg of plasmid DNA was mixed with 60% PG, 20% Ethanol and 20% waterand incubated at RT for 15 min before use.

To determine the efficiency of entrapment of the reporter genes, a DNAintercalation study with ethidium bromide was done to ensure that theDNA added has been entrapped in the liposomes. In brief, one ml ofethidium bromide (2 μg/ml) was added to an aliquot of the liposomepreparation containing DNA and mixed for three seconds in a vortexmixer. As positive and negative controls, DNA and ethidium bromide andethidium bromide alone were used. The ethidium bromide basedfluorescence of all samples was monitored in a fluorimeter at anemission wavelength of 595 nm.

In vivo Experiments on Rat Pups. Animal experiments were conducted onsix day old Harlan Sprague Dawley rat pups. 100 μl of the liposomeformulation containing the luciferase gene, or β-galactosidase gene, orone mg Nile Red (Fluorescent probe) was applied at 30 min intervals ontoa 1 square cm area of the back dorsal skin. Control pups received onlythe empty liposomes. After 24, 48 and 72 hours, the pups were sacrificedand the treated skin section was dissected out and used to analyze theexpression of reporter genes or the level of fluorescent probe.

In situ β-galactosidase assay. A portion of the skin section wasembedded in OCT, sectioned and fixed as 5 μm strips onto super frostslides with ice cold 1% formaldehyde, 0.2% glutaraldehyde, 2 mM MgCl2 inPBS. The fixed tissues were washed at RT for 2 hours in three changes ofPBS containing 2 mM MgCl₂, 0.1% sodium deoxycholate, 0.02% NP40. Thesewere subsequently stained in the dark at 37° C. for 16 hours in 2 mg/ml4-Cl-5-Br-3-indlyl-β-galactopyranoside (X-Gal), 5 mM potassiumferricyanide, 5 mm potassium ferrocyanide, 2 mm MgCl2, 0.02% NP40 and0.1% sodiumdeoxy cholate in PBS. At the end of the incubation period,the slides were washed with PBS and counterstained in hemotoxylin andeosin for histological examination.

Preparation of tissue homogenate. The dissected skin section was cutinto small pieces and homogenized in 2 ml of reporter lysis buffer(Promega) using a Polytron homogenizer. The homogenate was centrifugedat maximum speed for 15 min and the supernatant was used for furtheranalyses. Protein content of the homogenate was determined using the BCA(Pierce) method.

Quantitative analysis of β-galactosidase activity. β-galactosidaseactivity was measured by adding an aliquot of the tissue homogenate toan equal volume of 2× assay buffer (Promega), which contains thesubstrate (o-nitrophenyl-β-D-galactopyranoside). Samples were incubatedfor 30 min at 37° C. during which time the β-galactosidase enzymehydrolyzes the colorless substrate to 0-nitophenol, which is yellow. Thereaction was terminated by the addition of 1M sodium carbonate and theabsorbance was measured at 420 nm in a spectrophotometer. The activitywas expressed as units/mg protein.

Quantitative analysis of Luciferase activity. Luciferase activity wasmeasured in the tissue homogenate using the Dual Luciferase assay Kit(Promega) following the manufacturer's instructions. In brief, to 100 μlof the sample was added 100 μl of the Luciferase assay buffer containingthe substrate and the light emitted immediately after the addition ofStop&Glo buffer was measured in a luminometer. The activity wasexpressed as RLU/mg protein.

Nile Red. Fluorescence emission of Nile Red was observed under afluorescent microscope on skin sections.

Results:

Comparison of the efficiency of the delivery systems used. Theefficiency of the liposomal delivery systems was compared in terms ofthe expressed product β-galactosidase or Luciferase in the treated skinsection by measuring the activity of these two enzymes in the tissuehomogenate per mg of the protein extracted. FIG. 4 depicts theexpression of exogenous Luciferase in rats treated with the liposomalformulations. Rat pups treated with nonionic (NI) liposomesencapsulating 250 μg luciferase DNA showed maximum expression (95000RLU/mg protein) after 24 hours of treatment versus NI+DOTAP, and PLformulations. Interestingly, PINC polymer, PEG and the minoxidil carriersystem were found to be inefficient in the system described above. Asimilar trend was observed in the delivery of the β-galactosidase geneand the fluorescent Nile Red. The nonionic liposome formulation wasfound to be the most efficient delivery system when compared to otherdelivery systems (FIG. 5). Though the PEG-based minoxidil carrier systemalone was found to be an inefficient carrier system, subsequentexperiments have demonstrated that a 1:1 mixture of the nonionicliposome formulation and minoxidil carrier are as efficient or moreefficient than the nonionic liposome formulation alone in delivering theNile Red dye to follicle and epidermal cells.

These observations parallel the findings reported by Niemic et al(1997). They have reported that the perifollicular expression of humaninterleukin-1 receptor antagonist protein following topical applicationof liposome-plasmid DNA formulations was significantly higher withnonionic liposomes than phospholipid-based liposomes.

Composition of a preferred carrier substance to deliver chemoprotectivemolecules into the hair follicles. Having identified nonionic liposomesas the most efficient vehicle for transdermal delivery, studies wereconducted to deliver various chemoprotective molecules using nonionicliposomes as the carrier molecule, and the efficacy of each of thechemoprotectant molecules in conferring protection against chemotherapyinduced alopecia was determined on rat pups treated with Cytoxan.

The nonionic liposome preparations were prepared as described above.Immediately before use an equal volume of the chemoprotective inducermolecules (B-NF, BHA, CG09, Oltipraz, Sulphoraphane and tBHQ) in asuitable solvent was mixed with the liposomes and left at RT for 45 minbefore being used.

EXAMPLE 4 Microplate Assay for Rapid Screening of ChemoprotectiveInducing Agents

The Electrophile Responsive Element (EpRE) has been demonstrated tomediate the induced expression of phase II detoxifying enzymes andoxidative stress proteins which constitutes an important mechanism ofcancer chemoprevention. This example describes the development of arapid, cell-based, functional assay to screen and identify naturallyoccurring or synthetic chemicals with chemoprotective inducing activity.

Materials and Methods:

Chemicals and Reagents. BHA and TBHQ were purchased from Fluka Chemika(Milwaukee, Wis.). DMSO, β-NF, 3-MC and PDTC were purchased from SigmaChemical. Oltipraz was obtained from McKesson BioServices (Rockville,Md.). Sulforaphane was purchased from LKA Laboratories, Inc. (St. Paul,Minn.). Synthetic EpRE oligonucleotides were ordered from Integrated DNATechnologies (Coralville, Iowa). The Green Fluorescent Proteinexpression vector pEGFP was purchased from Clontech (Palo Alto, Calif.).A portion of the DIVERSet™ chemical library, containing 1100 small,hand-synthesized molecules, was purchased from ChemBridge Corporation(San Diego, Calif.).

Cell Culture. The human HepG2 hepatoma cell line was obtained from theAmerican Type Culture Collection (Rockville, Md.) and maintained in DMEMwith high glucose containing 10% fetal bovine serum supplemented with0.1% gentamicin (Life Technologies Inc., Gaithersburg, Md.). The cellswere grown at 37° C. in an humidified 5% CO₂/95% air atmosphere.

Construction of EpRE-TK-GFP Reporter Genes. Synthetic oligonucleotidescontaining a 41 bp EpRE motif were annealed and purified, and then withor without a 123 bp Thymidine-Kinase (TK) promoter fragment, wereinserted into the multiple cloning site of pEGFP generatingEpRE/TK/pEGFP and TK/pEGFP constructs, respectively. By concatamerizingthe 41 bp EpRE, multiple EpRE motif copies were also subcloned intopEGFP. The constructed plasmids were purified through Qiagen columns(Qiagen Inc, Santa Clarita, Calif.) and their sequence confirmed byrestriction analysis and sequencing which showed that the plasmidscontained EpRE and/or TK in the sense orientation.

Transfection Assay. HepG2 cells were seeded at a density of 10⁵ cells/60mm plate 24 hr prior to transfection. Cells were transfected with 2 μgEpRE/TK/pEGFP or TK/pEGFP plasmids using Lipofectin (Life Technologies,Gaithersburg, Md.) according to the manufacturer's instructions. Clonesresistant to 1 mg/ml G418 (Life Technologies, Grand Island, N.Y.) wereisolated. After 2-3 weeks, colonies were picked using a microscope andtransferred into wells of a 24-well plate for expansion.

Measurement of GFP and Screening Procedure. HepG2 cells (5×10⁴) wereseeded into wells of a black, clear bottom, tissue culture surface96-well plate (Becton Dickinson Labware, Franklin Lakes, N.J.) in orderto minimize background fluorescence, and after 24 hr then treated with aknown chemical or a test compound for an additional 24 hr. The DIVERSetchemical library compounds are packaged at 100¼ g/well as a dry film in96 well plates; after removing the shrinkwrap cover, they were dissolveddirectly in 100¼ l DMSO per well, and part of the compound solution wasthen further diluted in dilution plates with cell culture medium. Thefinal concentration of test compound in the HepG2 cell wells was around50¼M. The average molecular weight used for the test compounds was 300.β-NF and tBHQ, as positive controls, were added to wells of the HepG2plates at 10¼M and 90¼M, respectively. DMSO alone was added to controlcultures, and its concentration never exceeded 0.1% in positive controland 1.6% in test compound wells. After a 24 hr exposure to compounds,the medium was removed, 200 μl of PBS containing 100 μg/ml of EtBr wasadded to stain the HepG2 cells for 20 min at room temperature. The cellswere then washed with PBS and 200 μl PBS was added to the wells prior tomeasuring fluorescence. Measurement of GFP or EtBr fluorescence wasperformed using a fluorescence microplate reader (Molecular Dynamics,Sunnyvale, Calif.) with excitation/emission at 485 nm/530 nm and 485nm/612 nm, respectively. Captured data were transferred directly into anExcel computer file for direct data analysis.

Results:

Construction and Transfection of Reporter Genes. In the reporter geneconstructed for this screening system, an EpRE regulatory element and aTK promoter were inserted in front of the GFP reporter gene. In order toenhance the sensitivity of the reporter gene to the stimulus resultingfrom chemopreventive drug exposure, constructs containing increasingcopies of the EpRE element were also made, containing 1×, 2× and 4×copies of the 41 bp EpRE insert (FIG. 8). The fundamental assumption inthis screening system is that when cells are exposed to EpRE-activatingchemopreventive molecules, the level of intracellular GFP, whichreflects the extent to which gene expression is increased, reflects theinducing ability of the test compound. In a final step to creating thistest system, transfected HepG2 cell clones showing stable GFPexpression, both basal and induced, were isolated and used in thesubsequent screening steps.

Basal and Inducible Levels of GFP in HepG2 Cells. The basal andinducible expression levels of GFP in HepG2 cell clones which stablycarried reporter genes with different copy numbers of EpRE are shown inFIG. 2. In this experiment, we used tBHQ, one of the primary metabolitesof BHA, as the inducer molecule because it has been previously shown tobe a potent inducer of the expression of EpRE-dependent genes (Wasserman& Fahl, Proc. Natl. Acad. Sci. USA., 94: 5361-5366, 1997). Metabolicformation of tBHQ is generally considered to be the step responsible forthe anti-carcinogenic effects of BHA. There was no discernibledifference in the cell proliferation rates between parental HepG2 cellsand any of the selected clones that stably expressed the GFP reportergene. After measuring basal and induced GFP levels in 24 independentclones carrying the 4×EpRE reporter gene, the colony with the highestinducible expression of GFP and the lowest basal level, was used for thesubsequent chemical library screening assays.

DNA Content as an Internal Standard. Since known chemopreventivemolecules and library test compounds could become toxic at certainconcentrations and thus suppress cell growth in a given well of a testplate over the two days of drug exposure, it was desirable tostandardize the observed GFP level to some indicator of cell number ineach microtiter well. Measuring the DNA content of each well was adoptedas an internal cell standard. With a primary goal of maintainingscreening simplicity, when we considered the overlap of GFP emissionwavelength and other available methods used for detecting cell DNAcontent, we decided to use the DNA staining ability of the intercalatingmolecule EtBr for the rapid quantitative measurement of DNA content. Itwas very easy to measure the EtBr signal just by switching theexcitation/emission wavelengths in the fluorescence microplate reader.Correlation analysis indicated that there was an excellent correlationbetween EtBr intensity and cell number (FIG. 10, r=0.9). Therefore, GFPexpression levels for each standard and test compound were normalized tothe level of EtBr fluorescence found in each well to give a final GFPper cell value.

The Expression Level of GFP is Significantly Increased by KnownChemopreventive Molecules. To demonstrate that this cell-based assaycould be used to identify new chemopreventive molecules, we testedseveral of the currently studied chemopreventive molecules to determinehow sensitive the screening system would be in detecting them. As afirst step, the dose and time dependence of the GFP response followingtBHQ treatment were determined (FIG. 11). The level of greenfluorescence seen in the HepG2 reporter cells treated for 24 hr with 90μm tBHQ or 10 μM β-NF are shown in fluorescent images (FIG. 5). Profilesshowing the dose-dependent induction of reporter gene expression foreight different molecules are shown in FIG. 12. β-NF is a bifunctionalinducer, and it has been widely used in studies of the regulation ofboth phase I and phase II drug metabolizing genes. BHA, a syntheticphenolic antioxidant, is widely used as a food preservative. Dietaryadministration of higher doses of BHA has also been shown to conferprotection against a variety of chemical carcinogens, this effectattributed to the induction of many phase II detoxifying enzymes inrodents such as GSTs, epoxide hydrolases, and NQO1 (Benson et al.,Cancer Res., 38(12): 4486-95, 1978; Benson et al., Proc. Natl. Acad.Sci. USA., 77: 5216-20, 1980). Sulforaphane, isolated from broccoli, isa known inducer of phase II detoxifying enzymes and has been found toinhibit carcinogen-induced mammary tumors in rats (Zhang et al., Proc.Natl. Acad. Sci. USA., 91: 3147-50, 1994; Fahey & Talalay, Food & Chem.Toxicol., 37: 973-9, 1999). Oltipraz, an anti-schistosomal drug moleculewhich is a substituted 1,2-dithiole-3-thione, is an effective inhibitorof carcinogenesis in many rodent tissues and is an effective inducer ofphase II enzymes in vivo, in both humans and rodents (Clapper,Pharmacol. Therapeutics., 78: 17-27, 1998).

Screening of a Chemical Library. In a direct test of the reporterassay's ability to identify chemopreventive, inducing compounds, wescreened a chemical library using the described rapid screening assay.FIG. 7 shows a representative 3D graph, processed by computer analysis,that illustrates the induction ability of each test compound andpositive and negative control on a representative screening plate. A hitin the screening assay (Compound #09G06), showing induced GFP expression1.6-fold greater than that seen for the β-NF positive control wasidentified and is shown in FIG. 14.

EXAMPLE 5 Use of Liposome-Encapsulated Glutathione-S-Transferase toProtect Mammalian Epithelial Cells from the Toxic Effect of AlkylatineChemotherapeutic Agents

Glutathione-S-transferases (GSTs) are present as dimers in cells, withsubunit molecular weights in the range of from about 22-30 kDa, and areunable to cross cell membranes. Hence, a mechanism for intracellulardelivery of GSTs to target cells is needed to enhance their protectiveeffect during the course of alkylating drug treatment.

Liposomes have been shown to be a suitable non-toxic vehicle for thedelivery of drugs, immunogenic proteins, antibodies, DNA, RNA andenzymes, both in vivo and into cultured cells. In this example, wedemonstrate the utility of liposomes as an efficient delivery mechanismfor introducing large amounts of GSTs into mammalian cells, and theprotection conferred by this treatment from the damaging effect ofalkylating chemotherapeutic agents.

Described below is the use of cationic, pH-sensitive liposomes tomediate the efficient delivery of GSTs into the cytoplasm of mammaliancells. The studies were conducted using cultured mammalian epithelialcells, an appropriate model system to test the effectiveness ofliposome-entrapped detoxifying proteins in conferring protection tocells from drug toxicity.

Materials and Methods:

Preparation of liposomes. Dioleoyl phosphatidylcholine (DOPC), dioleoylphosphatidylethanolamine (DOPE),1,2-dioleoxyloxy-3-(trimethylamino)propane (DOTAP),1,2-dioleoyl-sn-3-succinylglycerol (DOSC),1,2-dipalmitoyl-sn-3-succinylglycerol (DPSG) were obtained from AvantiPolar Lipids (Birmingham, Ala.). Rat liver glutathione S-transferases(GSTs) were purchased from Sigma Chemical Co. (St. Louis, Mo.).

Lipid films were made by rotoevaporating the lipid in a chloroformsolution under argon gas. Large, multilamellar vesicles were prepared byhydrating (vortex mixing) the dry lipid film in 150 mM NaCl, 20 mM HEPES(pH 7.4) containing 0.2-5 mg of purified rat liver GSTs orFITC-conjugated rat liver GSTs (200 ng). The buffer temperature wasmaintained at a temperature that was approximately ten degrees above thegel-to-liquid-crystalline phase transition temperature of thephospholipid. Lipid concentrations of 50 mg/ml buffer were commonlyused. The frozen and thawed multilamellar vesicles were obtained byfreezing the large multilamellar vesicles from above in liquid nitrogenand thawing the sample in a water bath at the same temperature used forhydration.

The frozen and thawed large multilamellar vesicles were extruded using astainless steel extrusion device (Lipex Biomembranes, Vancouver, BC)equipped with a 10 ml water-jacketed barrel attached to circulatingwater bath which allowed extrusion at elevated temperatures. Thevesicles were equilibrated at the appropriate temperature for at least15 min prior to extrusion. Extrusions were performed through twopolycarbonate filters of pore sizes ranging from 100-400 nm in diameterat nitrogen pressures of up to 800 psi. The preparations were subjectedto ten repeated cycles through the extruder before usage.

The resulting liposomes were separated from unencapsulated GST bygel-filtration on a Bio-Gel A-15m Gel(Bio-Rad, CA) column (20 cmlength×2 cm dia). The fractions containing liposomes were concentratedby spinning for 30 min on a centriprep-500 concentrator (Amicon, Inc.,MA).

Cellular uptake of liposomes. Monolayers of COS-7 and AGS cells weregrown in Dulbecco's modified Eagle's medium with high glucose (DMEM)/10%(vol/vol) fetal bovine serum in 50-mm culture dishes at 37° C. Prior toliposome exposure, cell monolayers were washed 2 times with DMEM. Thecells were then incubated at 37° C. for various lengths of time (0.5-5hr) in medium containing liposomes. Cell monolayers were washed fourtimes with PBS (phosphate-buffered saline). To quantitatively determinethe uptake of FITC-labeled GST in the liposomes by the cells, cellmonolayers were thoroughly washed in PBS, scraped off the culturedishes, and lysed in 1 ml of lysis buffer (10 mM Tris-HCL+1% Tritonx-100). After centrifuging for 10 min in an Eppendorf centrifuge, thecleared supernatant of the cell extract was retained. The fluorescenceassociated with this cytosolic extract was then measured using afluorescence spectrophotometer and converted to units FITC-GSTinternalized based upon a standard curve obtained with the known amountof FITC-labeled rat liver GST.

Exposure of GST-containing cells to antineoplastic drugs. COS-7 or AGScells were seeded in 96-well plates and grown overnight in Dulbecco'smodified Eagle's medium with high glucose (DMEM-HG) supplemented with10% (vol/vol) fetal bovine serum (FBS). The following day, cells werewashed with serum-free DMEM-HG. Liposomes in DMEM-HG were added to thecell monolayers and incubated 4 hours at 37° C. At the end of theincubation period, monolayers were washed with DMEM-HG supplemented with10% FBS to remove free liposomes. The antineoplastic drug melphalan wasdiluted in phenol red-free DMEM-HG containing 10% FBS at the desiredconcentration and added to the cell monolayers. The multiwell plateswere then incubated at 37° C. for 72 hours. Upon completion of theincubation period, the drug-containing medium was removed, and the cellswere washed with phenol red-free and FBS-free DMEM-HG to remove residualserum. Cell proliferation was assessed by measuring the conversion ofthe soluble yellow dye MTT(3-[4,5-Dimethylthiazol-2-y]-2,5-diphenyltetrazolium bromide, SigmaChemical, St. Louis, Mo.) to an insoluble purple precipitate by livingcells. MTT was dissolved at 5 mg/ml in PBS and passed through a 20 μmfilter to remove impurities. MTT stock solution was diluted 1:4 inphenol red-free FBS-free DMEM-HG, and 200 μl of this dilution was addedto each well of the plate. The plates were incubated 4 hours at 37° C.in the dark, then blotted to remove the MTT solution. The converted dyewas solubilized by the addition of 200 μl of acid isopropanol (1.6 mlconcentrated HCL in 500 ml isopropanol) to each well of the plate.Absorbance of converted dye was measured at a wavelength of 570 nm withbackground subtraction at 690 nm.

Results:

Delivery of liposome-encapsulated detoxifying protein to cells. Theefficiency of the delivery of detoxifying protein to cells was assessedby quantitating the fluorescence of tagged protein found in the cytosol.When PC liposomes were employed, cells received from about 60-175% moreof the fluorescently labeled protein than when no liposomes wereemployed. Delivery by cationic liposomes (PC+DOTAP) resulted in anincrease in fluorescence of from about six to eight fold, relative todelivery by PC liposomes.

Protection of cells by exposure to liposome-encapsulated detoxifyingprotein. Incubation of COS cells with liposome-encapsulated GST prior totreatment with melphalan, an alkylating antineoplastic agent, conferredprotection to the cells. A high MTT absorbance is correlated with a lowrate of cell death. Cells not treated with liposome-encapsulated GST hadan MTT absorbance that was from about 2 to 25 times lower than that ofcells pretreated with liposome-encapsulated GST.

These results demonstrate that pretreatment of epithelial cells withGST-containing liposomes prior to exposure to antineoplasiic agentsprotects cells against the cytotoxic effects of these agents. In view ofthe success in protecting cells using GST alone, it is further expectedthat liposomes comprising both GST and glutathione will be even moreeffective in protecting cells from the toxic effects of alkylatingchemotherapeutic agents, by virtue of providing an additional supply ofsubstrate to increase the activity rate of the GST.

EXAMPLE 6 Modification of Liposomes to Target the GastrointestinalEpithelium

In the setting of the gut, the incorporation of additional means toallow attachment of the liposomes to the epithelial cell surface wouldfacilitate delivery of liposomal contents to these cells. To increasethe specificity of liposomes for lumenal epithelial cells that line thestomach and upper small intestine, the cholera toxin B (CTB) subunit maybe covalently attached to the surface of a liposome. Liposomes that havethe CTB subunit attached to their surface attach with specificity tocells that express the M1 ganglioside receptor molecule on theirsurface. Cells that normally express this cell surface molecule includelumenal epithelial cells lining the stomach and upper small intestine.This is the means by which cholera bacterial cells attach to these cellsin a natural infection. The B subunit of cholera toxin confers M1ganglioside receptor binding, but in the absence of the A subunit,confers no toxicity.

Materials and Methods:

Liposome preparation for conjugation to cholera toxin B subunit.Liposomes containing purified rat liver GSTs and trace FITC-conjugatedrat liver GST were prepared and purified by the standard extrusionprotocol described in Example 1, using the following mixture of lipids:phosphatidylcholine (PC): phosphatidylethnolamine (PE):1,2-Dioleoyl-sn-glycero-3phosphaethanolamine-N-[4]-(p-maleimidophenyl)butyrate (N-MBP-PE),70:20:10 Mol %.

Chemical modification of cholera toxin B subunit (CTB) for cross-linkingto liposomes. A primary amine reactive reagent was used to add thiolgroups to the lysine residues of CTB. The thiol groups were necessaryfor reaction with the maleimide group on the N-MPB-PE-containingliposomes. To achieve this, CTB (100 μg) was dissolved in HEPES-salinebuffer and incubated with N-succinimidyl 3-(2-pyridyldithio)propionate(SPDF) at a 1:100 molar ratio in the dark at room temperature for onehour. The reaction was quenched by adding 10 μl of 20 mM L-lysine in 20mM Tris-HCl (pH 6.8) and the reaction products were then reduced byadding 5 μl of 7.7 mg/ml dithiothreitol in water. Unreacted substanceswere removed by passing the reaction mixture through a size exclusionSephadex G25 spin column. The concentration of the activated CTB in theexcluded fraction was measured by Coomassie protein assay reagent(Pierce Biochemical, Rockford, Ill.).

Cross-linking of activated CTB to liposomes. Conjugation of activatedCTB to liposomes containing GST and trace FITC-conjugated GST wascarried out by incubating the reduced CTB (50 μg) with a suspension of 1mL N-MBP-PE-bearing liposomes at 5° C. overnight. The coupling reactionwas stopped by adding 10 μl of L-cysteine buffer (20 mM L-cysteine in 20mM Tris-HCL buffer, pH7.2). The CTB-conjugated liposomes were purifiedfrom unconjugated CTB on a size exclusion gel filtration column (BiogelA-15m gel, Bio-Rad Laboratories, CA; 15 cm long×2 cm diameter)pre-equilibrated with HEPES-saline buffer. The liposomes were eluted in0.5 ml fractions and the liposome content of each fraction wasdetermined by fluorescence and GST activity. Liposome-containingfractions were pooled (fractions #5-9) and concentrated to 1 ml bycentrifugation at 1000×g for 30 min using a Centriprep 500 concentrator(Amicon Inc., Beverly Mass.).

Cellular uptake of CTB liposomes. Cells (6×10⁶ HuTu or COS cells) wereseeded into 60 mm dishes and grown overnight in DMEM with high glucose(DMEM w/HG) supplemented with 10% fetal calf serum (FCS) in a humidifiedatmosphere of 10% CO₂. The monolayers were then washed three times with5 ml of DMEM w/HG+HEPES saline (50 mM HEPES+50 mM NaCl, ph 7.5). To testthe ability of the CTB-conjugated liposomes to bind specifically tocells bearing the GM1 ganglioside receptor, some dishes were pretreatedfor 10 min with a commercially-available sample of GM1 gangliosidereceptor (20 μg). A 100 μl sample of CTB-conjugated liposomes(containing 5000 fluorescence units of FITC-conjugated GST) was added toeach monolayer with 5 ml DMEM w/HG+HEPES saline buffer, and incubatedfor 4 hours at 37° C. The cell monolayers were then washed 4 times with5 ml PBS to remove unbound CTB-conjugated liposomes. The amount ofCTB-conjugated liposomes bound/internalized to the cells was quantifiedby first scraping the cells from the culture dish, resuspending in 0.3ml PBS and sonicating for 30 seconds. A 20 μl aliquot of each celllysate was added to 2 ml of PBS, and the amount of cell-associatedfluorescence was measured (excitation/emission maxima 494/520 nm) in afluorometer. The concentration of protein in the cell lysate wasdetermined using the Coomassie protein estimation kit.

Results:

The use of liposomes having the CTB subunit attached to the liposomesurface resulted in enhanced delivery of labeled protein togastrointestinal carcinoma cells (HuTu cells), but not to kidney tubuleepithelial cells. (COS cells). The increased efficiency conferred by theCTB subunit was quenched in the presence of an excess of free M1Ganglioside receptor. These results demonstrate that liposomes areeffectively modified to target cells of the gastrointestinal epitheliumby incorporation of the CTB subunit onto their surfaces.

The present invention is not limited to the embodiments described andexemplified above, but is capable of variation and modification withoutdeparture from the scope of the appended claims.

1. A method for reducing or preventing hair loss in a patient caused byadministration of a chemotherapeutic agent comprising cyclophosphamide,the method comprising administering to the patient's cells lining hairfollicles an effective amount and for an effective duration apharmaceutical preparation comprising a compound according to thestructure

and one or more nonionic liposomes, wherein the chemoprotective inducingagent induces or increases production of glutathione-S-transferase Ya.